Well completion spacer fluids containing fibers and methods

ABSTRACT

Well completion spacer fluids containing fibers and methods of using the spacer fluids are provided. A method of the invention for displacing a first fluid from a well bore with an incompatible second fluid comprises the following steps. A spacer fluid is placed between the first and second fluids to separate the first and second fluids and to remove the first fluid from the walls of the well bore. Thereafter, the first fluid and the spacer fluid are displaced from the well bore with the second fluid. The spacer fluid comprises water, a weighting material, a dispersing agent, a suspending agent and friction reducer and fibers. The spacer fluid containing the components mentioned above is preferably also foamed.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 10/393,965 filed on Mar. 21, 2003.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to spacer fluids containing fibersand methods of using the spacer fluids in well completions such asprimary cementing.

[0004] 2. Description of the Prior Art

[0005] Well bores are commonly drilled using the rotary drilling method.In that method, a drill bit connected to a drill string is rotated whiledrilling fluid is circulated through the drill string, through the drillbit and upwardly to the surface through the annulus between the drillstring and the walls of the well bore being drilled. The drilling fluidfunctions to cool the drill bit, to remove cuttings from the well boreand to maintain hydrostatic pressure on the well bore. The hydrostaticpressure prevents formation fluids from entering the well bore duringdrilling.

[0006] The drilling fluid also forms a filter cake on the walls of thewell bore which prevents the drilling fluid from being lost intopermeable subterranean zones. However, the drilling fluid in the filtercake dehydrates and gels thereby forming a layer of solids and gelleddrilling fluid on the walls of the well bore. While this filter cake isadvantageous during drilling, it is detrimental to obtaining effectivedrilling fluid displacement and removal from the walls of the well bore.

[0007] In primary well cementing operations, a hydraulic cement slurryis pumped into the annular space between the walls of the well bore andthe exterior surfaces of a pipe string disposed therein. The cementslurry is allowed to set in the annular space thereby forming an annularsheath of hardened substantially impermeable cement therein. The cementsheath physically supports and positions the pipe in the well bore andbonds the exterior surfaces of the pipe to the walls of the well borewhereby the undesirable migration of fluids between zones or formationspenetrated by the well bore is prevented. If the drilling fluid filtercake is not adequately removed from the walls of the well bore orportions thereof, a competent seal between the hardened cement and thewell bore does not result.

[0008] Spacer fluids are typically placed between two fluids containedor to be pumped within well bores. Examples of fluids between whichspacer fluids are utilized include between hydraulic cement slurries anddrilling fluids, between different drilling fluids during drilling fluidchangeouts and between drilling fluids and completion brines. Thespacers are also utilized to enhance drilling fluid and filter cakeremoval from the walls of well bores, to enhance displacement efficiencyand to physically separate chemically incompatible fluids. For example,a hydraulic cement slurry and drilling fluid are separated by a spacerfluid when the cement slurry is placed in the annulus between a pipestring and the walls of a well bore. The spacer fluid preventsintermixing of the cement slurry and the drilling fluid and facilitatesthe removal of filter cake and gelled drilling fluid from the walls ofthe well bore during displacement of the drilling fluid by the cementslurry. If intermixing of the cement slurry and the drilling fluidoccurs, viscous masses are formed in the annulus that prevent continueddisplacement.

[0009] The heretofore utilized spacer fluids have achieved varyingdegrees of success in displacing fluids and removing filter cake, gelleddrilling fluid and the like from the walls of the well bore. However,there is a continuing need for improved spacer fluids that achievegreater removal of drilling fluid and filter cake from the walls of thewell bore and prevent mixing of incompatible fluids.

SUMMARY OF THE INVENTION

[0010] The present invention provides improved water based wellcompletion spacer fluids containing fibers and methods of using thespacer fluids which meet the need described above and overcome thedeficiencies of the prior art. The presence of fibers in the spacerfluids of this invention increases the drilling fluid and filter cakeremoval from the walls of a well bore as a result of the fibersimparting abrasive properties to the spacer fluids. In addition, thespacer fluids are preferably foamed which increases the drilling fluidand filter cake removal. That is, the foamed spacer fluids of thisinvention exhibit better drilling fluid and drilling fluid filter cakeremoval as a result of the gas in the foamed spacer fluids energizingthe fluids. The gas bubbles are compressed as a foamed spacer fluid ispumped down the pipe string and the hydrostatic pressure increases. Asthe foamed spacer fluid enters the annulus and is pumped toward thesurface, the hydrostatic pressure decreases which allows the gas bubblesto expand and cause the foamed spacer fluid to achieve highly efficientdrilling fluid and filter cake removal from the annulus. The expansionof the gas bubbles also allows the foamed spacer fluid and fiberstherein to enter irregular hole configurations and enlarged holes in thewell bore and remove drilling fluid and filter cake therefrom. Finally,the increased viscosity of a foamed spacer fluid provides enhancedsuspension of removed drilling fluid and filter cake. The water-basedspacer fluids of this invention are particularly well suited fordisplacing water-based drilling fluids and other water-based fluids, butthey can also be used effectively in the removal of oil based drillingfluids and other oil based fluids. When a foamed spacer fluid of thisinvention contacts an oil based drilling fluid, the foamed spacer fluidwill convert to a non-foamed spacer fluid. However, it is believed thatthe released gas enters the filter cake which in conjunction with thefibers in the spacer fluid facilitates the removal of the filter cake.

[0011] The spacer fluids of this invention basically comprise water, aweighting material, a dispersing agent, a suspending agent and frictionreducer, and fibers. The foamed spacer fluids comprise water, aweighting material, a dispersing agent, a suspending agent and frictionreducer, fibers, a foaming and foam stabilizing surfactant or mixture ofsurfactants and a gas.

[0012] The methods of this invention basically comprise the followingsteps. A spacer fluid is placed between first and second fluids in awell bore to separate the first and second fluids and to remove thefirst fluid from the walls of the well bore, the spacer fluid comprisingwater, a weighting material, a dispersing agent, a suspending agent andfriction reducer, and fibers. Thereafter, the first fluid and the spacerfluid are displaced from the well bore by the second fluid.

[0013] A preferred method of the invention comprises the followingsteps. A foamed spacer fluid is placed between first and second fluidsin a well bore to separate the first and second fluids and to remove thefirst fluid from the walls of the well bore, the spacer fluid comprisingwater, a weighting material, a dispersing agent, a suspending agent andfriction reducer, fibers, a foaming and foam stabilizing surfactant ormixtures of surfactants and a gas. Thereafter, the first fluid and thespacer fluid are displaced from the well bore by the second fluid.

[0014] The objects, features and advantages of the present inventionwill be readily apparent to those skilled in the art upon a reading ofthe description of preferred embodiments which follows.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0015] As stated above, the spacer fluids of this invention basicallycomprise water, a weighting material, a dispersing agent, a suspendingagent and friction reducer, and fibers. A more preferred foamed spacerfluid comprises water, a weighting material, a dispersing agent, asuspending agent and friction reducer, fibers, a foaming and foamstabilizing surfactant or mixtures of surfactants and a gas.

[0016] The water in the spacer fluids of this invention can be freshwater or salt water. The term “salt water” is used herein to meanunsaturated salt solutions and saturated salt solutions including brinesand seawater.

[0017] Examples of weighting materials that can be utilized in thespacer fluids include, but are not limited to, barium sulfate, hematite,manganese tetraoxide and calcium carbonate. Of these, barium sulfate ispreferred. The weighting material is included in the spacer fluids in anamount in the range of from about 0 pounds to about 745 pounds perbarrel of water therein.

[0018] The dispersing agent is included in the spacer fluids to dispersethe solids and other materials in the water. Examples of dispersingagents that can be utilized include, but are not limited to, naphthalenesulfonate condensed with formaldehyde, sodium polyacrylate, a terpolymerof acrylic acid, alkyloxybenzene sulfonate and methally sulfonate,formaldehyde, acetone, bisulfate condensate, melamine sulfonateformaldehyde condensate, and mixtures thereof. The dispersing agent isincluded in the spacer fluid in an amount in the range of from about0.5% to about 5% by weight of the water therein.

[0019] The suspending agent and friction reducer is included in thespacer fluid to suspend the weighting material and other solids thereinas well as to reduce friction during pumping of the spacer fluid.Examples of suspending agent and friction reducers that can be utilizedinclude, but are not limited to, sepiolite, whelan gum, xanthan gum,hydroxyethylcellulose, bentonite, attapulgite, and mixtures thereof. Ofthese, xanthan gum is preferred. The suspending agent and frictionreducer is included in the spacer fluid in an amount in the range offrom about 2 pounds to about 10 pounds per barrel of water therein.

[0020] A variety of fibers can be utilized in the present invention.Examples of preferred such fibers include, but are not limited to,polyester fibers, polyamide fibers, polyethylene fibers, polypropylenefibers, and other polyolefin fibers. The fibers can be made hydrophilicby treating them with a surface active agent. Of the foregoing,hydrophilic polypropylene fibers are most preferred. The fibers areincluded in the spacer fluid in an amount in the range of from about{fraction (1/16)} pound to about {fraction (1/4)} pound per barrel ofspacer fluid.

[0021] When the spacer fluid is a foamed spacer fluid, a foaming andfoam stabilizing surfactant that functions to facilitate the formationof a foam and to stabilize the foam during its use is included in thespacer fluid. While various such surfactants known to those skilled inthe art can be used, presently preferred such surfactants include, butare not limited to, a mixture of an ethoxylated alcohol ether sulfatesurfactant, an alkyl or alkene amidopropyl betaine surfactant and analkyl or alkene amidopropyl dimethyl amine oxide surfactant or a mixtureof an alpha-olefinic sulfonate surfactant and an alkyl or alkeneamidopropyl betaine surfactant. Of these, the mixture of an ethoxylatedalcohol ether sulfate surfactant, an alkyl or alkene amidopropyl betainesurfactant and an alkyl or alkene amidopropyl dimethyl amine oxidesurfactant is preferred. This mixture and others are described in detailin U.S. Pat. Nos. 6,063,738; 6,210,476; 5,897,699; 5,875,845; and5,820,670 issued to Chatterji, et al. which are incorporated herein byreference thereto. The mixture of foaming and foam stabilizingsurfactants is included in the foamed spacer fluid in an amount in therange of from about 0.5% to about 5% by weight of the water therein.

[0022] Also, when the spacer fluid is foamed, a gas such as air ornitrogen is included in the spacer fluid. The gas is preferably nitrogenand the gas is present in the foamed spacer fluid in an amount in therange of from about 5% to about 80% by volume of the water therein.

[0023] The spacer fluids of this invention can also optionally include awell bore scouring material to facilitate the removal of filter cake andgelled drilling fluid from the walls of the well bore. Examples ofsuitable scouring materials include, but are not limited to,diatomaceous earth, crystalline silica, amorphous silica, and mixturesthereof. Of these, crystalline silica scouring material is preferred.When used, the scouring material is present in the spacer fluid in anamount in the range of from about 10 pounds to about 80 pounds perbarrel of water therein.

[0024] Also, when the spacer fluid is not foamed, it can optionallyinclude a defoamer comprising oil and silica present in an amount in therange of from about 0.5% to about 2% by weight of the water therein.

[0025] As mentioned above, the spacer fluids of this invention areparticularly useful in primary cementing operations wherein the foamedspacer fluid is placed between a drilling fluid and a hydraulic cementslurry. The drilling fluid can be a water-based drilling fluid, an oilbased drilling fluid or a foamed water or oil based drilling fluid.

[0026] The hydraulic cement slurry can include various cements includingPortland cements, slag cements, pozzolana cements, gypsum cements,aluminous cements, silica cements or high alkalinity cements. Of these,Portland cement is generally preferred. The water in the hydrauliccement slurry can be fresh water or salt water.

[0027] When the spacer fluid of this invention is batch mixed on thesurface, a spacer mixing aid is added to the spacer fluid in a smallamount to facilitate complete suspension of the heavy weight materialstherein. The spacer mixing aid is comprises 39.5% xanthan gum, 48.3%mineral oil, 2.7% oleophilic clay; 5.9% nonylphenol ethoxylated with 3moles of ethylene oxide, and 3.9% naphthalene sulfonate condensed withformaldehyde (percents are by weight). The spacer mixing aid is notrequired when the spacer fluid is mixed on-the-fly.

[0028] A preferred method of this invention for displacing a first fluidfrom a well bore with an incompatible second fluid comprises the stepsof: (a) placing a spacer fluid between the first and second fluids toseparate the first and second fluids and to remove the first fluid fromthe walls of the well bore, the spacer fluid comprising water, aweighting material, a dispersing agent, a suspending agent and frictionreducer, and fibers; and (b) displacing the first fluid and the foamedspacer fluid from the well bore with the second fluid.

[0029] A preferred method of displacing drilling fluid from a well borewith a hydraulic cement slurry comprises the steps of: (a) placing afoamed spacer fluid between the drilling fluid and the hydraulic cementslurry to separate the drilling fluid from the hydraulic cement slurryand to remove the drilling fluid and filter cake from the walls of thewell bore, the foamed spacer fluid comprising water, a weightingmaterial, a dispersing agent, a suspending agent and friction reducer,fibers, a foaming and foam stabilizing surfactant and a gas; and (b)displacing the drilling fluid and the foamed spacer fluid from the wellbore with the hydraulic cement slurry.

[0030] A preferred spacer fluid of this invention comprises: water; aweighting material;

[0031] a dispersing agent; a suspending agent and friction reducer; andfibers.

[0032] A preferred foamed spacer fluid of this invention comprises:water; a weighting material; a dispersing agent; a suspending agent andfriction reducer; fibers; a foaming and foam stabilizing surfactant; anda gas.

[0033] In order to further illustrate the methods and foamed spacerfluids of this invention, the following examples are given.

EXAMPLE 1

[0034] Various spacer fluids were tested using a spacer fluid efficiencytest apparatus designed to indicate how efficiently a spacer fluid willerode a filter cake from a formation core. A diagram of the testapparatus and the test procedure followed is set forth below.

[0035] The test apparatus shown above consists of a reservoir, variablespeed pump, test cell containing the core with the filter cake depositedon it and flexible tubing connecting the components.

[0036] Test Procedure:

[0037] The following test procedure is used to evaluate the efficiencyof the spacer to remove the filter cake from the core.

[0038] 1. Drilling fluid is placed into a standard API high pressurefluid loss test apparatus containing a core as the filter medium.

[0039] 2. A filter cake is deposited on a core using a standard API highpressure fluid loss test apparatus.

[0040] 3. The test cell containing the drilling fluid and core isdisassembled.

[0041] The drilling fluid is removed from the cell.

[0042] The end with the core is removed and the outside of the corerinsed to remove any drilling fluid that is fluid surrounding the core.

[0043] The filter cake is rinsed by pouring water over it gently.

[0044] The weight of the core and filter cake is determined.

[0045] 4. The test cell is reassembled and both ends sealed.

[0046] 5. The spacer to be tested is poured into the reservoir.

[0047] The pump speed control is adjusted to allow the pump to move thespacer through the lines and across the filter cake at 3.3 liters perminute.

[0048] The inlet and outlets for the flow of the spacer through the testcell is level with the top of the core.

[0049] The circulation of the spacer is continued for 40 minutes.

[0050] At the end of 40 minutes, the circulation is stopped.

[0051] 6. The test cell is disassembled again.

[0052] The bottom end holding the core with the filter cake on it isremoved.

[0053] The sides of the core are rinsed using the same procedure as atthe start of the test.

[0054] The top of the filter cake is rinsed by gently pouring water overit to remove loose spacer, the same as was done to remove loose drillingfluid at the beginning of the test.

[0055] The weight of the core and filter cake is then determined.

[0056] The filter cake is then removed from the core.

[0057] The weight of the core (without the filter cake) is determined.

[0058] 7. The percent filter cake removed is then determined by:

% Rem=(CW _(B) −CW _(A))+CW _(B)

[0059] Where:

[0060] % Rem=Percent filter cake removed

[0061] CW_(B)=Filter Cake Weight before exposure to spacer

[0062] CW_(A)=Filter Cake Weight after exposure to spacer

[0063] A first spacer fluid (Spacer 1) having a density of 16 pounds pergallon was prepared comprising water; 39.23% by weight of water ofdiatomaceous earth scouring material; 35.0% by weight of water ofcrystalline sand scouring material; 11.76% by weight of water ofsepiolite suspending agent and friction reducer; 9.8% by weight of waterof naphthalene sulfonate condensed with formaldehyde dispersing agent;1.96% by weight of water of an oil and silica defoaming agent; and 1gallon of spacer mixing aid blend per 10 barrels of mixing water. To thefirst spacer fluid, ⅛ pound of hydrophilic polypropylene fibers perbarrel of spacer fluid was added. The spacer mixing aid blend isincluded in the spacer when it is batch mixed.

[0064] A 16 pound per gallon spacer fluid (Spacer 1) having the samecomposition as the first spacer fluid described above without the fiberswas prepared and foamed with 2% by weight of a surfactant mixturecomprising an ethoxylated alcohol either sulfate, an alkyl or alkeneamidopropyl betaine and an alkyl or alkene amidopropyl dimethyl amineoxide to 10, 12 and 14 pound per gallon foamed spacer fluids. 10, 12 and14 pound per gallon foamed spacer fluids with hydrophilic polypropylenefibers were also prepared.

[0065] A second spacer fluid (Spacer 2) having a density of 16 poundsper gallon was prepared comprising water; 6.0% by weight of water ofsodium polyacrylate dispersing agent; 3.75% by weight of water of aterpolymer of acrylic acid, alkoxybenzene sulfonate and methallysulfonate dispersing agent; 1.5% by weight of water of whelan gumsuspending agent and friction reducer; 0.5% by weight of water ofhydroxyethylcelluclose suspending agent and friction reducer; 22.5% byweight of water of sepiolite suspending agent and friction reducer;66.0% by weight of water of amorphous silica. To the second spacerfluid, ⅛ pound of hydrophilic polypropylene fibers per barrel was added.

[0066] A 16 pound per gallon spacer fluid (Spacer 2) having the samecomposition as the second spacer fluid described above without thefibers was prepared and foamed with the same surfactant mixturedescribed above to 10, 12 and 14 pound per gallon foamed spacer fluids.10, 12 and 14 pound per gallon foamed spacer fluids with hydrophilicpolypropylene fibers were also prepared.

[0067] The results of spacer fluid efficiency tests using the testapparatus described above are set forth in Table I below (Spacer 1 and11 pound per gallon water based drilling fluid to deposit filter cake)and Table II below (Spacer 2 and 12.5 pound per gallon water baseddrilling fluid to deposit filter cake). TABLE I Filter Cake Erosion BySpacer 1 Fluids With and Without Fibers Drilling Weight Fluid ofDrilling Filter Fluid After Percent of Cake Spacer 1 Spacer 1 FilterCake Weight, Fluid Circulation, Removal After grams Tested grams Spacer1 Circulation 24 14 lb/gal 24 0 (No Fibers) 22 14 lb/gal 20 10 (WithFibers) 19 14 lb/gal 15 21 (Foamed, No Fibers) 31 14 lb/gal 27 13(Foamed, With Fibers) 28 12 lb/gal 26 7 (Foamed, No Fibers) 24 12 lb/gal19 21 (Foamed, With Fibers) 29 10 lb/gal 27 7 (Foamed, No Fibers) 28.510 lb/gal 26.2 8 (Foamed, With Fibers)

[0068] From Table I, it can be seen that the presence of fibers in thenon-foamed and foamed spacer fluids provides greater efficiency inremoving drilling fluid. TABLE II Filter Cake Erosion By Spacer 2 FluidsWith and Without Fibers Weight of Drilling Percent of Fluid After FilterCake Drilling Fluid Spacer 2 Spacer 2 Removal After Filter Cake FluidCirculation, Spacer 2 Weight, grams Tested grams Circulation 18.5 16lb/gal 17.7 4 (No Fibers) 19.8 16 lb/gal 18.0 9 (With Fibers) 12.8 14lb/gal 12.7 1 (Foamed, No Fibers) 15.4 14 lb/gal 13.7 11 (Foamed, WithFibers) 16.9 12 lb/gal 14.7 13 (Foamed, No Fibers) 15.9 12 lb/gal 13.018 (Foamed, With Fibers) 23.5 10 lb/gal 20.8 11 (Foamed, No Fibers) 19.210 lb/gal 16.8 12.5 (Foamed, With Fibers)

[0069] From Table II, it can again be seen that the presence of fibersin the non-foamed and foamed spacer fluids provides greater efficiencyin removing drilling fluid.

What is claimed is:
 1. A method of displacing a first fluid from a wellbore with an incompatible second fluid comprising the steps of: placinga spacer fluid between said first and second fluids to separate saidfirst and second fluids and to remove said first fluid from the walls ofsaid well bore, said spacer fluid comprising water, a weightingmaterial, a dispersing agent, a suspending agent and friction reducer,and fibers; and displacing said first fluid and said spacer fluid fromsaid well bore with said second fluid.
 2. The method of claim 1 whereinsaid water is selected from the group consisting of fresh water and saltwater.
 3. The method of claim 1 wherein said weighting material isselected from the group consisting of barium sulfate, hematite,manganese tetraoxide and calcium carbonate.
 4. The method of claim 1wherein said weighting material is barium sulfate.
 5. The method ofclaim 1 wherein said weighting material is present in said spacer fluidin an amount in the range of from about 0 pounds to about 745 pounds perbarrel of said water therein.
 6. The method of claim 1 wherein saiddispersing agent is selected from the group consisting of naphthalenesulfonate condensed with formaldehyde, sodium polyacrylate, a terpolymerof acrylic acid, alkyloxybenzene sulfonate and methally sulfonate,formaldehyde, acetone, bisulfate condensate, melamine sulfonateformaldehyde condensate, and mixtures thereof.
 7. The method of claim 1wherein said dispersing agent is naphthalene sulfonate condensed withformaldehyde.
 8. The method of claim 1 wherein said dispersing agent ispresent in said spacer fluid in an amount in the range of from about0.5% to about 5% by weight of said water therein.
 9. The method of claim1 wherein said suspending agent and friction reducer is selected fromthe group consisting of sepiolite, whelan gum, xanthan gum, hydroxyethylcellulose, bentonite, attapulgite, and mixtures thereof.
 10. The methodof claim 1 wherein said suspending agent and friction reducer is xanthangum.
 11. The method of claim 1 wherein said suspending agent andfriction reducer is present in said spacer fluid in an amount in therange of from about 2 pounds to about 10 pounds per barrel of said watertherein.
 12. The method of claim 1 wherein said fibers are selected fromthe group consisting of polyester fibers, polyamide fibers, polyethylenefibers, polypropylene fibers, and other polyolefin fibers.
 13. Themethod of claim 1 wherein said fibers are hydrophilic polypropylenefibers.
 14. The method of claim 1 wherein said fibers are present insaid spacer fluid in an amount in the range of from about ¼ pound toabout {fraction (1/4)} pound per barrel of spacer fluid.
 15. The methodof claim 1 wherein said spacer fluid further comprises a well bore wallscouring material selected from the group consisting of diatomaceousearth, crystalline silica, amorphous silica, and mixtures thereof. 16.The method of claim 15 wherein said scouring material is amorphoussilica.
 17. The method of claim 15 wherein said scouring material ispresent in said spacer fluid in an amount in the range of from about 10pounds to about 80 pounds per barrel of said water therein.
 18. Themethod of claim 1 wherein said spacer fluid further comprises adefoamer.
 19. The method of claim 18 wherein said defoamer comprises oiland silica.
 20. The method of claim 18 wherein said defoamer is presentin said spacer fluid in an amount in the range of from about 0.5% toabout 2% by weight of said water therein.
 21. The method of claim 1wherein said spacer fluid further comprises a spacer mixing aid blend.22. The method of claim 21 wherein said spacer mixing aid blendcomprises xanthan gum, mineral oil, olephilic clay, nonylphenol withthree moles of ethylene oxide, and a naphthalene sulfonate condensedwith formaldehyde dispersing agent.
 23. The method of claim 1 whereinsaid spacer fluid further comprises a foaming and foam stabilizingsurfactant and a gas whereby said spacer fluid is foamed.
 24. The methodof claim 23 wherein said foaming and foam stabilizing surfactant is amixture of an ethoxylated alcohol ether sulfate surfactant, an alkyl oralkene amidopropyl betaine surfactant and an alkyl or alkene amidopropyldimethyl amine oxide surfactant.
 25. The method of claim 23 wherein saidfoaming and foam stabilizing surfactant is present in said foamed spacerfluid in an amount in the range of from about 0.5% to about 5% by weightof said water therein.
 26. The method of claim 23 wherein said gas isnitrogen.
 27. The method of claim 23 wherein said gas is present in saidfoamed spacer fluid in an amount in the range of from about 5% to about80% by volume of said water therein.
 28. The method of claim 1 whereinsaid first fluid is a drilling fluid.
 29. The method of claim 28 whereinsaid drilling fluid is selected from the group consisting of water baseddrilling fluids, oil based drilling fluids and foamed water based or oilbased drilling fluids.
 30. The method of claim 1 wherein said secondfluid is a hydraulic cement slurry comprising water and cement.
 31. Themethod of claim 30 wherein said hydraulic cement is selected from thegroup consisting of Portland cements, slag cements, pozzolana cements,gypsum cements, aluminous cements, silica cements and alkaline cements.32. The method of claim 30 wherein said cement is Portland cement. 33.The method of claim 30 wherein said water is selected from the groupconsisting of fresh water and salt water.
 34. A method of displacingdrilling fluid from a well bore with a hydraulic cement slurrycomprising the steps of: placing a foamed spacer fluid between saiddrilling fluid and said hydraulic cement slurry to separate saiddrilling fluid from said hydraulic cement slurry and to remove drillingfluid and filter cake from the walls of said well bore, said foamedspacer fluid comprising water, a weighting material, a dispersing agent,a suspending agent and friction reducer, fibers, a foaming and foamstabilizing surfactant, and a gas whereby said spacer fluid is foamed;and displacing said drilling fluid and said foamed spacer fluid fromsaid well bore with said hydraulic cement slurry.
 35. The method ofclaim 34 wherein said water is selected from the group consisting offresh water and salt water.
 36. The method of claim 34 wherein saidweighting material is selected from the group consisting of bariumsulfate, hematite, manganese tetraoxide and calcium carbonate.
 37. Themethod of claim 34 wherein said weighting material is barium sulfate.38. The method of claim 34 wherein said weighting material is present insaid spacer fluid in an amount in the range of from about 0 pounds toabout 745 pounds per barrel of said water therein.
 39. The method ofclaim 34 wherein said dispersing agent is selected from the groupconsisting of naphthalene sulfonate condensed with formaldehyde, sodiumpolyacrylate, a terpolymer of acrylic acid, alkyloxybenzene sulfonateand methally sulfonate, formaldehyde, acetone, bisulfate condensate,melamine formaldehyde condensate, and mixtures there.
 40. The method ofclaim 34 wherein said dispersing agent is naphthalene sulfonatecondensed with formaldehyde.
 41. The method of claim 34 wherein saiddispersing agent is present in said spacer fluid in an amount in therange of from about 0.5% to about 5% by weight of said water therein.42. The method of claim 34 wherein said suspending agent and frictionreducer is selected from the group consisting of sepiolite, whelan gum,xanthan gum, hydroxyethyl cellulose, bentonite, attapulgite, andmixtures thereof.
 43. The method of claim 34 wherein said suspendingagent and friction reducer is xanthan gum.
 44. The method of claim 34wherein said suspending agent and friction reducer is present in saidspacer fluid in an amount in the range of from about 2 pounds to about10 pounds per barrel of said water therein.
 45. The method of claim 34wherein said fibers are selected from the group consisting of polyesterfibers, polyamide fibers, polyethylene fibers, polypropylene fibers, andother polyolefin fibers.
 46. The method of claim 34 wherein said fibersare hydrophilic polypropylene fibers.
 47. The method of claim 34 whereinsaid fibers are present in said spacer fluid in an amount in the rangeof from about {fraction (1/16)} pound to about {fraction (1/4)} poundper barrel of spacer fluid.
 48. The method of claim 34 wherein saidfoaming and foam stabilizing surfactant is a mixture of an ethoxylatedalcohol ether sulfate surfactant, an alkyl or alkene amidopropyl betainesurfactant and an alkyl or alkene amidopropyl dimethyl amine oxidesurfactant.
 49. The method of claim 34 wherein said foaming and foamstabilizing surfactant is present in said foamed spacer fluid in anamount in the range of from about 0.5% to about 5% by weight of saidwater therein.
 50. The method of claim 34 wherein said gas is nitrogen.51. The method of claim 34 wherein said gas is present in said foamedspacer fluid in an amount in the range of from about 5% to about 80% byvolume of said water therein.
 52. The method of claim 34 wherein saiddrilling fluid is selected from the group consisting of water baseddrilling fluids, oil based drilling fluids and foamed water based or oilbased drilling fluids.
 53. The method of claim 34 wherein said hydrauliccement is selected from the group consisting of Portland cements, slagcements, pozzolana cements, gypsum cements, aluminous cements, silicacements and alkaline cements.
 54. The method of claim 34 wherein saidcement is Portland cement.
 55. The method of claim 34 wherein said waterin said slurry is said water is selected from the group consisting offresh water and salt water.
 56. A spacer fluid comprising: water; aweighting material; a dispersing agent; a suspending agent and frictionreducer; and fibers.
 57. The spacer fluid of claim 56 wherein said wateris selected from the group consisting of fresh water and salt water. 58.The spacer fluid of claim 56 wherein said weighting material is selectedfrom the group consisting of barium sulfate, hematite, manganesetetraoxide and calcium carbonate.
 59. The spacer fluid of claim 56wherein said weighting material is barium sulfate.
 60. The spacer fluidof claim 56 wherein said weighting material is present in said spacerfluid in an amount in the range of from about 0 pounds to about 745pounds per barrel of said water therein.
 61. The spacer fluid of claim56 wherein said dispersing agent is selected from the group consistingof naphthalene sulfonate condensed with formaldehyde, sodiumpolyacrylate, a terpolymer of acrylic acid, alkyloxybenzene sulfonateand methally sulfonate, formaldehyde, acetone, bisulfate condensate,melamine sulfonate formaldehyde condensate, and mixtures thereof. 62.The spacer fluid of claim 56 wherein said dispersing agent isnaphthalene sulfonate condensed with formaldehyde.
 63. The spacer fluidof claim 56 wherein said dispersing agent is present in said spacerfluid in an amount in the range of from about 0.5% to about 5% by weightof said water therein.
 64. The spacer fluid of claim 56 wherein saidsuspending agent and friction reducer is selected from the groupconsisting of sepiolite, whelan gum, xanthan gum, hydroxyethylcellulose, bentonite, attapulgite, and mixtures thereof.
 65. The spacerfluid of claim 56 wherein said suspending agent and friction reducer isxanthan gum.
 66. The spacer fluid of claim 56 wherein said suspendingagent and friction reducer is present in said spacer fluid in an amountin the range of from about 2 pounds to about 10 pounds per barrel ofsaid water therein.
 67. The spacer fluid of claim 56 wherein said fibersare selected from the group consisting of polyester fibers, polyamidefibers, polyethylene fibers, polypropylene fibers, and other polyolefinfibers.
 68. The spacer fluid of claim 56 wherein said fibers arehydrophilic polypropylene fibers.
 69. The spacer fluid of claim 56wherein said fibers are present in said spacer fluid in an amount in therange of from about {fraction (1/16)} pound to about {fraction (1/4)}pound per barrel of spacer fluid.
 70. The spacer fluid of claim 56wherein said spacer fluid further comprises a well bore wall scouringmaterial selected from the group consisting of diatomaceous earth,crystalline silica, amorphous silica, and mixtures thereof.
 71. Thespacer fluid of claim 56 wherein said scouring material is amorphoussilica.
 72. The spacer fluid of claim 56 wherein said scouring materialis present in said spacer fluid in an amount in the range of from about10 pounds to about 80 pounds per barrel of said water therein.
 73. Thespacer fluid of claim 56 wherein said spacer fluid further comprises adefoamer.
 74. The spacer fluid of claim 56 wherein said defoamercomprises oil and silica.
 75. The spacer fluid of claim 56 wherein saiddefoamer is present in said spacer fluid in an amount in the range offrom about 0.5% to about 2% by weight of said water therein.
 76. Afoamed spacer fluid comprising: water; a weighting material; adispersing agent; a suspending agent and friction reducer; fibers; afoaming and foam stabilizing surfactant; and a gas.
 77. The foamedspacer fluid of claim 76 wherein said water is selected from the groupconsisting of fresh water and salt water.
 78. The foamed spacer fluid ofclaim 76 wherein said weighting material is selected from the groupconsisting of barium sulfate, hematite, manganese tetraoxide and calciumcarbonate.
 79. The foamed spacer fluid of claim 76 wherein saidweighting material is barium sulfate.
 80. The foamed spacer fluid ofclaim 76 wherein said weighting material is present in said spacer fluidin an amount in the range of from about 0 pounds to about 745 pounds perbarrel of said water therein.
 81. The foamed spacer fluid of claim 76wherein said dispersing agent is selected from the group consisting ofnaphthalene sulfonate condensed with formaldehyde, sodium polyacrylate,a terpolymer of acrylic acid, alkyloxybenzene sulfonate and methallysulfonate, formaldehyde, acetone, bisulfate condensate, melaminesulfonate formaldehyde condensate, and mixtures thereof.
 82. The foamedspacer fluid of claim 76 wherein said dispersing agent is naphthalenesulfonate condensed with formaldehyde.
 83. The foamed spacer fluid ofclaim 76 wherein said dispersing agent is present in said spacer fluidin an amount in the range of from about 0.5% to about 5% by weight ofsaid water therein.
 84. The foamed spacer fluid of claim 76 wherein saidsuspending agent and friction reducer is selected from the groupconsisting of sepiolite, whelan gum, xanthan gum, hydroxyethylcellulose, bentonite, attapulgite, and mixtures thereof.
 85. The foamedspacer fluid of claim 76 wherein said suspending agent and frictionreducer is xanthan gum.
 86. The foamed spacer fluid of claim 76 whereinsaid suspending agent and friction reducer is present in said spacerfluid in an amount in the range of from about 2 pounds to about 10pounds per barrel of said water therein.
 87. The foamed spacer fluid ofclaim 76 wherein said fibers are selected from the group consisting ofpolyester fibers, polyamide fibers, polyethylene fibers, polypropylenefibers, and other polyolefin fibers.
 88. The foamed spacer fluid ofclaim 76 wherein said fibers are hydrophilic polypropylene fibers. 89.The foamed spacer fluid of claim 76 wherein said fibers are present insaid spacer fluid in an amount in the range of from about {fraction(1/16)} pound to about {fraction (1/4)} pound per barrel of said spacerfluid.
 90. The foamed spacer fluid of claim 76 wherein said spacer fluidfurther comprises a well bore wall scouring material selected from thegroup consisting of diatomaceous earth, crystalline silica, amorphoussilica, and mixtures thereof.
 91. The foamed spacer fluid of claim 76wherein said scouring material is amorphous silica.
 92. The foamedspacer fluid of claim 76 wherein said scouring material is present insaid spacer fluid in an amount in the range of from about 10 pounds toabout 80 pounds per barrel of said water therein.
 93. The foamed spacerfluid of claim 76 wherein said foaming and foam stabilizing surfactantis a mixture of an ethoxylated alcohol ether sulfate surfactant, analkyl or alkene amidopropyl betaine surfactant and an alkyl or alkeneamidopropyl dimethyl amine oxide surfactant.
 94. The foamed spacer fluidof claim 76 wherein said foaming and foam stabilizing surfactant ispresent in said foamed spacer fluid in an amount in the range of fromabout 0.5% to about 5% by weight of said water therein.
 95. The foamedspacer fluid of claim 76 wherein said gas is nitrogen.
 96. The foamedspacer fluid of claim 76 wherein said gas is present in said foamedspacer fluid in an amount in the range of from about 5% to about 80% byvolume of said water therein.
 97. A method of displacing fluids in awell bore comprising: placing a foamed spacer fluid comprising fibersbetween first and second fluids; and displacing said first fluid andsaid spacer fluid from the well bore with said second fluid.
 98. Themethod of claim 97 wherein said spacer fluid comprises water selectedfrom the group consisting of fresh water and salt water.
 99. The methodof claim 97 wherein said spacer fluid comprises a weighting materialselected from the group consisting of barium sulfate, hematite,manganese tetraoxide and calcium carbonate.
 100. The method of claim 99wherein said weighting material is present in said spacer fluid in anamount in the range of from about 0 pounds to about 745 pounds perbarrel of said water therein.
 101. The method of claim 97 wherein saidspacer fluid comprises a dispersing agent selected from the groupconsisting of naphthalene sulfonate condensed with formaldehyde, sodiumpolyacrylate, a terpolymer of acrylic acid, alkyloxybenzene sulfonateand methally sulfonate, formaldehyde, acetone, bisulfate condensate,melamine sulfonate formaldehyde condensate, and mixtures thereof. 102.The method of claim 101 wherein said dispersing agent is present in saidspacer fluid in an amount in the range of from about 0.5% to about 5% byweight of said water therein.
 103. The method of claim 97 wherein saidspacer fluid comprises a suspending agent and friction reducer selectedfrom the group consisting of sepiolite, whelan gum, xanthan gum,hydroxyethyl cellulose, bentonite, attapulgite, and mixtures thereof.104. The method of claim 103 wherein said suspending agent and frictionreducer is present in said spacer fluid in an amount in the range offrom about 2 pounds to about 10 pounds per barrel of said water therein.105. The method of claim 97 wherein said spacer fluid comprises fibersselected from the group consisting of polyester fibers, polyamidefibers, polyethylene fibers, polypropylene fibers, hydrophilicpolypropylene fibers, and other polyolefin fibers.
 106. The method ofclaim 105 wherein said fibers are present in said spacer fluid in anamount in the range of from about ¼ pound to about {fraction (1/4)}pound per barrel of spacer fluid.
 107. The method of claim 97 whereinsaid spacer fluid further comprises a well bore wall scouring materialselected from the group consisting of diatomaceous earth, crystallinesilica, amorphous silica, and mixtures thereof.
 108. The method of claim107 wherein said scouring material is amorphous silica.
 109. The methodof claim 107 wherein said scouring material is present in said spacerfluid in an amount in the range of from about 10 pounds to about 80pounds per barrel of said water therein.
 110. The method of claim 97wherein said spacer fluid further comprises a defoamer.
 111. The methodof claim 110 wherein said defoamer comprises oil and silica.
 112. Themethod of claim 110 wherein said defoamer is present in said spacerfluid in an amount in the range of from about 0.5% to about 2% by weightof said water therein.
 113. The method of claim 97 wherein said spacerfluid further comprises a spacer mixing aid blend.
 114. The method ofclaim 113 wherein said spacer mixing aid blend comprises xanthan gum,mineral oil, olephilic clay, nonylphenol with three moles of ethyleneoxide, and a naphthalene sulfonate condensed with formaldehydedispersing agent.
 115. The method of claim 97 wherein said spacer fluidfurther comprises a foaming and foam stabilizing surfactant and a gaswhereby said spacer fluid is foamed.
 116. The method of claim 115wherein said foaming and foam stabilizing surfactant is a mixture of anethoxylated alcohol ether sulfate surfactant, an alkyl or alkeneamidopropyl betaine surfactant and an alkyl or alkene amidopropyldimethyl amine oxide surfactant.
 117. The method of claim 115 whereinsaid foaming and foam stabilizing surfactant is present in said foamedspacer fluid in an amount in the range of from about 0.5% to about 5% byweight of said water therein.
 118. The method of claim 115 wherein saidgas is nitrogen.
 119. The method of claim 115 wherein said gas ispresent in said foamed spacer fluid in an amount in the range of fromabout 5% to about 80% by volume of said water therein.
 120. The methodof claim 97 wherein said first fluid is a drilling fluid.
 121. Themethod of claim 120 wherein said drilling fluid is selected from thegroup consisting of water based drilling fluids, oil based drillingfluids and foamed water based or oil based drilling fluids.
 122. Themethod of claim 97 wherein said second fluid is a hydraulic cementslurry comprising water and cement.
 123. The method of claim 122 whereinsaid hydraulic cement is selected from the group consisting of Portlandcements, slag cements, pozzolana cements, gypsum cements, aluminouscements, silica cements and alkaline cements.
 124. The method of claim122 wherein said water is selected from the group consisting of freshwater and salt water.
 125. A well completion fluid comprising a foamedspacer fluid containing fibers.
 126. The fluid of claim 125 wherein saidspacer fluid comprises water selected from the group consisting of freshwater and salt water.
 127. The fluid of claim 125 wherein said spacerfluid comprises a weighting material selected from the group consistingof barium sulfate, hematite, manganese tetraoxide and calcium carbonate.128. The fluid of claim 127 wherein said weighting material is presentin said spacer fluid in an amount in the range of from about 0 pounds toabout 745 pounds per barrel of said water therein.
 129. The fluid ofclaim 125 wherein said spacer fluid comprises a dispersing agentselected from the group consisting of naphthalene sulfonate condensedwith formaldehyde, sodium polyacrylate, a terpolymer of acrylic acid,alkyloxybenzene sulfonate and methally sulfonate, formaldehyde, acetone,bisulfate condensate, melamine sulfonate formaldehyde condensate, andmixtures thereof.
 130. The fluid of claim 129 wherein said dispersingagent is present in said spacer fluid in an amount in the range of fromabout 0.5% to about 5% by weight of said water therein.
 131. The fluidof claim 125 wherein said spacer fluid comprises a suspending agent andfriction reducer selected from the group consisting of sepiolite, whelangum, xanthan gum, hydroxyethyl cellulose, bentonite, attapulgite, andmixtures thereof.
 132. The fluid of claim 131 wherein said suspendingagent and friction reducer is present in said spacer fluid in an amountin the range of from about 2 pounds to about 10 pounds per barrel ofsaid water therein.
 133. The fluid of claim 125 wherein said fibers areselected from the group consisting of polyester fibers, polyamidefibers, polyethylene fibers, polypropylene fibers, hydrophilicpolypropylene fibers, and other polyolefin fibers.
 134. The fluid ofclaim 125 wherein said fibers are present in said spacer fluid in anamount in the range of from about {fraction (1/16)} pound to about{fraction (1/4)} pound per barrel of spacer fluid.
 135. The fluid ofclaim 125 wherein said spacer fluid further comprises a well bore wallscouring material selected from the group consisting of diatomaceousearth, crystalline silica, amorphous silica, and mixtures thereof. 136.The fluid of claim 135 wherein said scouring material is amorphoussilica.
 137. The fluid of claim 135 wherein said scouring material ispresent in said spacer fluid in an amount in the range of from about 10pounds to about 80 pounds per barrel of said water therein.
 138. Thefluid of claim 125 wherein said spacer fluid further comprises adefoamer.
 139. The fluid of claim 138 wherein said defoamer comprisesoil and silica.
 140. The fluid of claim 138 wherein said defoamer ispresent in said spacer fluid in an amount in the range of from about0.5% to about 2% by weight of said water therein.